# agar

/ˈeɪɡɝ/ (US) · /ˈeɪɡɑː/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/agar
Updated: 2026-08-15

## Definition

a jelly-like substance made from seaweed. Scientists use it in labs to grow bacteria, and cooks use it to thicken food.

For teachers: a gelatinous substance obtained from various kinds of red algae. Used primarily as a solidifying agent in culture media for microbiological research and as a vegan alternative to gelatin in food preparation.

## Examples

- The scientist put the bacteria on a plate of agar.
- The lab technician prepared several petri dishes with nutrient-rich agar to test the water samples for contamination.
- Because it remains solid at higher temperatures than gelatin, agar is the preferred medium for incubating human pathogens that require a stable environment at body temperature.

## Usage notes

- Typically uncountable when referring to the substance; can be countable when referring to specific types or prepared plates.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.